Apparatus and method for semi distributed resource allocation in a cognitive radio wireless communication system

1. A method of operating a User Terminal (UT) in a Cognitive Radio (CR) wireless communication system, the method comprising: determining whether a signal of a licensed system is detected in at least one frequency band used by the CR wireless communication system, wherein the licensed system is a system that has priority of the at least one frequency band; when the signal of the licensed system is detected, determining, by a controller, a per-subcarrier Transmit (Tx) power according to a water filling mechanism in such a manner that a sum rate is maximized without exceeding a current maximum Tx power; upon receiving a binary message requesting to regulate the maximum Tx power from a Base Station (BS), determining, by the controller, a Penalty Factor (PF) based on at least one of the current maximum Tx power, the per-subcarrier Tx power, a per-subcarrier data rate, a minimum required data rate, and a threshold coefficient for a maximum allowed data rate; and regulating a new maximum Tx power by multiplying the PF by the current maximum Tx power.

2. The method of claim 1 , wherein the determining of the PF comprises: determining a Power Penalty (PP) parameter which is in proportion to a sum of the per-subcarrier Tx power for all subcarriers allocated to the UT and which is in inverse proportion to the current maximum Tx power; determining a Rate Penalty (RP) parameter which increases with an increase of a sum of a ratio of a data rate for each subcarrier to the minimum required data rate and which decreases with an increase of the maximum allowed data rate coefficient; determining a Fairness Gain (FG) parameter which is in proportion to the data rate for each subcarrier and a sum of the per-subcarrier Tx power and which is in inverse proportion to the sum of the per-subcarrier data rate and the Tx power of each subcarrier; determining a first value which is an inverse number of a value obtained by subtracting the FG parameter from a sum of the RP parameter and the PP parameter; and determining as the PF a smaller value between 1 and a greater value between the first value and a second value, wherein the second value is a predetermined minimum value of the PF.

3. The method of claim 2 , wherein the PP parameter is calculated according to: PP i = ∑ k ∈ S i ⁢ P i , k P i max , i = 1 , 2 , … ⁢ , L , where PP i denotes a Power Penalty (PP) parameter of a UTi, k denotes a subcarrier index, S i denotes a subcarrier set allocated to the UTi, P i,k denotes power used for a subcarrier k of the UTi, P i max denotes maximum power of the UTi, and L denotes a number of UTs.

4. The method of claim 2 , wherein the RP parameter is calculated according to: RP i = log ( ∑ k ∈ S i ⁢ R i , k / R i min ) log ⁡ ( ɛ ) , i = 1 , 2 , … ⁢ , L , where RPi denotes a RP parameter of a UTi, R i,k denotes a data rate at a subcarrier k, R i min denotes a minimum data rate of the UTi, S i denotes a subcarrier set allocated to the UTi, εdenotes a threshold coefficient for a maximum allowed data rate, and L denotes a number of UTs.

5. The method of claim 2 , wherein the FG parameter is calculated according to: FG i = ∏ k ∈ S i ⁢ ⁢ λ i , k , i = 1 , 2 , … ⁢ , L , where FGi denotes a FG parameter of a UTi, S i denotes a subcarrier set allocated to the UTi, λ i,k denotes a quality indicator for a subcarrier k of the UTi, and L denotes a number of UTs.

6. The method of claim 2 , wherein the PF is calculated according to: PF i ⁡ ( s + 1 ) = [ 1 RP i ⁡ ( s ) + PP i ⁡ ( s ) - FG i ⁡ ( s ) ] PF i min 1 , i = 1 , 2 , … ⁢ , L , and wherein s denotes an iteration count index and PF i min denotes a minimum value of the PF.

7. The method of claim 1 , further comprising, when uplink data is transmitted after regulating the maximum Tx power, transmitting the PF to the BS.

8. The method of claim 1 , wherein determining the per-subcarrier Tx power according to the water filling mechanism comprises considering the current maximum Tx power and a Power Spectral Mask (PSM) for avoiding interference to the licensed system.

9. The method of claim 1 , further comprising: persistently sensing the signal of the licensed system while performing communication.

10. The method of claim 1 , further comprising: receiving, by the UT, a report indicating that the licensed system is activated when the signal of the licensed system is detected.

11. A User Terminal (UT) apparatus in a Cognitive Radio (CR) wireless communication system, the apparatus comprising: a controller configured to determine whether a signal of a licensed system is detected in at least one frequency band used by the CR wireless communication system, wherein the licensed system is a system that has priority of the at least one frequency band; wherein the controller further is configured to: determine a per-subcarrier Transmit (Tx) power according to a water filling mechanism in such a manner that a sum rate is maximized without exceeding a current maximum Tx power when the signal of the licensed system is detected, determine, upon receiving a binary message requesting to regulate the maximum Tx power from a Base Station (BS), a Penalty Factor (PF) based on at least one of the current maximum Tx power, the per-subcarrier Tx power, a per-subcarrier data rate, a minimum required data rate, and a threshold coefficient for a maximum allowed data rate, and regulate a new maximum Tx power by multiplying the PF by the current maximum Tx power.

12. The apparatus of claim 11 , wherein the controller is further configured to: determine a Power Penalty (PP) parameter which is in proportion to a sum of the per-subcarrier Tx power for all subcarriers allocated to the UT and which is in inverse proportion to the maximum Tx power, determine a Rate Penalty (RP) parameter which increases with an increase of a sum of a ratio of a data rate for each subcarrier to the minimum required data rate and which decreases with an increase of the maximum allowed data rate coefficient, determine a Fairness Gain (FG) parameter which is in proportion to the data rate for each subcarrier and a sum of the per-subcarrier Tx power and which is in inverse proportion to the sum of the per-subcarrier data rate and the Tx power of each subcarrier, determine a first value which is an inverse number of a value obtained by subtracting the FG parameter from a sum of the RP parameter and the PP parameter, and determine as the PF a smaller value between 1 and a greater value between the first value and a second value, wherein the second value is a predetermined minimum value of the PF.

13. The apparatus of claim 12 , wherein the PP parameter is calculated according to: PP i = ∑ k ∈ S i ⁢ P i , k P i max , i = 1 , 2 , … ⁢ , L , where PP i , denotes a Power Penalty (PP) parameter of a UTi, k denotes a subcarrier index, S i denotes a subcarrier set allocated to the UTi, P i,k denotes power used for a subcarrier k of the UTi, P i max denotes maximum power of the UTi, and L denotes a number of UTs.

14. The apparatus of claim 12 , wherein the RP parameter is calculated according to: RP i = log ( ∑ k ∈ S i ⁢ R i , k / R i min ) log ⁡ ( ɛ ) , i = 1 , 2 , … ⁢ , L , where RPi denotes a RP parameter of a UTi, R i,k denotes a data rate at a subcarrier k, R i min denotes a minimum data rate of the UTi, S i denotes a subcarrier set allocated to the UTi, εdenotes a threshold coefficient for a maximum allowed data rate, and L denotes a number of Uts.

15. The apparatus of claim 12 , wherein the FG parameter is calculated according to: FG i = ∏ k ∈ S i ⁢ ⁢ λ i , k , i = 1 , 2 , … ⁢ , L , where FGi denotes a FG parameter of a UTi, S i denotes a subcarrier set allocated to the UTi, λ i,k denotes a quality indicator for a subcarrier k of the UTi, and L denotes a number of UTs.

16. The apparatus of claim 12 , wherein the PF is calculated according to: PF i ⁡ ( s + 1 ) = [ 1 RP i ⁡ ( s ) + PP i ⁡ ( s ) - FG i ⁡ ( s ) ] PF i min 1 , i = 1 , 2 , … ⁢ , L , and wherein s denotes an iteration count index and PF i min denotes a minimum value of the PF.

17. The apparatus of claim 11 , further comprising a transmitter configured to transmit the PF to the BS when uplink data is transmitted after regulating the maximum Tx power.

18. The apparatus of claim 11 , wherein determining the per-subcarrier Tx power according to the water filling mechanism comprises considering the current maximum Tx power and a Power Spectral Mask (PSM) for avoiding interference to the licensed system.

19. The apparatus of claim 11 , wherein the controller is configured to: persistently sense the signal of the licensed system while performing communication.

20. The apparatus of claim 11 , wherein the controller is configured to: receive, from the base station, a report indicating that the licensed system is activated when the signal of the licensed system is detected.